As described by Tullis et al. in "Particle-Free Dockable Interface for Integrated Circuit Processing", U.S. patent application Ser. No. 536,600 filed Sept. 28, 1983, now Pat. No. 4,532,970, and by Thrasher et al. in "Standardized Mechanical Interface System for Integrated Circuit Processing", U.S. patent application Ser. No. 536.599 filed Sept. 28, 1983, abandoned and by Tullis in "Interlocking Door Latch for Dockable Interface for Integrated Circuit Processing", U.S. patent application Ser. No. 594,498 filed Mar. 29, 1984, now Pat. No. 4,534,389, a standardized mechanical interface (SMIF) system has been demonstrated for the fabrication of integrated circuits (ICs). The SMIF system reduces particle contamination during storage, transport and transfer in IC fabrication by mechanically minimizing the volume of gaseous media surrounding IC wafers during fabrication, insuring that much of this gas is essentially stationary relative to the wafers, and insuring that particles from exterior "ambient" environments cannot enter the wafer environment. Experiments have shown that the SMIF system of wafer handling reduces wafer particle contamination by as much as ten times when compared to conventional Class 100 clean room wafer handling practice.
Typically in the SMIF system, as shown in FIG. 1, a cassette 10 holding wafers 20 in cassette slots (not shown) is transferred through an interface port between a SMIF box 30 and a SMIF environment under a canopy 40 by means of a SMIF elevator 50. Once inside the canopy 40, the cassette 10 is transferred to an equipment cassette elevator 60 which is part of a piece of processing equipment 70 in which the wafers 20 are to be processed. After processing, the wafers 20 are transferred back into the cassette 10 and the cassette 10 is transferred from the equipment elevator 60 of the processing equipment 70 to the SMIF elevator 50 which in turn transfers the cassette 10 back into the SMIF box 30. In some processing equipment 70, wafer handlers (not shown) place the processed wafers 20 in the cassette 10 with the wafers 20 protruding some distance out of the cassette slots. In other cases wafers 20 can slide on the cassette slots due to vibration or jerky motions of the processing equipment 70. In either case it is important to push the wafers 20 all the way into the cassette 10 before the SMIF elevator 50 is raised to transfer the cassette 10 into the SMIF box 30.
Formerly there have been two ways of transferring cassettes between SMIF elevators and equipment elevators while making sure that the wafers are pushed fully into the cassette. As shown in FIG. 1, a cassette manipulator 80 can be manually manipulated by an operator from outside of the SMIF canopy 40. Such a manipulator 80 is advantageous in that its motion within the canopy 40 does not cause undesired particle stirring and contamination of the wafers 20. Unfortunately, such a manipulator 80 requires a high degree of manual dexterity to place the cassette 10 in the desired location. A second approach, as shown in FIG. 2, is the use of a sealed glove 210 as in a conventional glove box attached to one wall 220 of the SMIF canopy 40 in order to transfer cassettes 10 between the SMIF elevator 50 and the equipment elevator 60. The glove box solution requires only a moderate degree of manual dexterity to transfer cassettes between the SMIF elevator 50 and the equipment elevator 60 while ensuring that all of the wafers 20 are pushed fully into the cassette 10. However, the glove box solution is strictly manual and the motion of the glove 210 can cause undesirable particle stirring within the SMIF canopy 40.